Water treatment device, water treatment system, and water treatment method

Abstract

The water treatment device (10) comprises a first separation tank (1) that receives wastewater (11) and separates it into a first effluent and a first precipitate (15), a reaction tank (2) that receives the first effluent and brings the first effluent into contact with microorganisms to cause a reaction, and a second separation tank that receives the reaction water from the reaction tank and separates the reaction water into a second effluent and a second precipitate (12). The water treatment device further comprises a precipitate transformation section (4) that takes in at least a portion of the second precipitate and generates a modified precipitate (14) by transforming flocs, which are an aggregate of microorganisms contained in the second precipitate, and transports the modified precipitate to the first separation tank or upstream of the first separation tank and mixes it with the wastewater.

Description

[Technical field]

[0001] The present disclosure relates to a water treatment device, a water treatment system, and a water treatment method. [Background technology]

[0002] Wastewater such as sewage is first separated and removed from solids in a primary settling tank, then sent to a reaction tank containing activated sludge, a collection of microorganisms called flocs, where oxygen is supplied while organic matter, nitrogen, etc. are biologically treated by the activated sludge, and this activated sludge is separated and removed in a final settling tank before being discharged into rivers, etc., or reused. The solids and activated sludge separated and removed in the primary and final settling tanks during this water treatment are collected as sediments, and efforts are being made to use them as energy. Patent Document 1 discloses that a mixer is provided for mixing excess sludge generated in biological treatment with organic wastewater as raw water, and the excess sludge is mixed with the organic wastewater and subjected to solid-liquid separation in a primary sedimentation tank, thereby increasing the amount of methane gas generated from the recovered sludge. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2016 / 148086 Summary of the Invention [Problem to be solved by the invention]

[0004] However, although the amount of organic matter recovered in the primary sedimentation tank increases by mixing oxygen-supplied excess sludge with organic wastewater, there was an issue that the organic matter recovery rate was low when simply mixing oxygen-supplied excess sludge with organic wastewater.

[0005] The present disclosure has been made to solve the above-mentioned problems, and aims to provide a water treatment device capable of improving the recovery rate of organic matter in the treatment of organic wastewater, as well as a water treatment system and a water treatment method using the same. [Means for solving the problem]

[0006] The water treatment device according to the present disclosure includes a first separation tank that receives wastewater and separates it into a first effluent and a first precipitate, a reaction tank that receives the first effluent and brings the first effluent into contact with microorganisms to cause a reaction, and a second separation tank that receives the reaction water from the reaction tank and separates the reaction water into a second effluent and a second precipitate, and further includes a precipitate transformation unit that takes in at least a portion of the second precipitate and generates a modified precipitate by transforming flocs, which are an aggregate of microorganisms contained in the second precipitate, and transports the modified precipitate to the first separation tank or upstream of the first separation tank and mixes it with wastewater. The sediment conversion unit generates a negative pressure in the circulated second sediment to introduce at least one of a gas and a liquid. It is characterized by:

[0007] In addition, the water treatment system according to the present disclosure includes a water treatment device according to the present disclosure, a concentration device that concentrates precipitate including at least a first precipitate transferred from the water treatment device to form concentrated sludge, and a digester that heats the concentrated sludge to decompose organic matter in the concentrated sludge and generate digester gas.

[0008] The water treatment method according to the present disclosure further includes a first separation step of receiving wastewater and separating it into a first effluent and a first precipitate, a reaction step of receiving the first effluent and contacting the first effluent with microorganisms to cause a reaction, a second separation step of receiving reaction water obtained in the reaction step and separating the reaction water into a second effluent and a second precipitate, and a second separation step of taking in at least a portion of the second precipitate. A negative pressure is generated in the circulated second precipitate to introduce at least one of a gas and a liquid into the second precipitate. The method includes a precipitate transformation step for generating a modified precipitate by transforming the state of flocs, which are an aggregate of microorganisms contained in the second precipitate, and a mixing step for mixing the generated modified precipitate with wastewater to incorporate and precipitate organic matter in the wastewater. Effect of the Invention

[0009] According to the present disclosure, by returning the modified precipitate obtained by modifying the second precipitate to the first separation tank or upstream of the first separation tank, a larger amount of organic matter contained in the wastewater can be precipitated in the first precipitate, and the recovery amount of the first precipitate separated in the first separation tank can be increased, i.e., the recovery rate of the organic matter recovered as the first precipitate can be improved. [Brief description of the drawings]

[0010] [Figure 1] 1 is a schematic configuration diagram of a water treatment device according to a first embodiment. [Diagram 2] FIG. 2 is an image diagram of generating metamorphosed flocs according to the first embodiment. [Diagram 3] FIG. 2 is an image diagram showing how flocs according to the first embodiment adsorb organic matter. [Figure 4] FIG. 2 is an image diagram showing how the modified flocs according to the first embodiment adsorb organic matter. [Diagram 5] 2 is a schematic configuration diagram showing an example of a precipitate transformation section according to the first embodiment. FIG. [Figure 6] 1 is a schematic diagram of an apparatus for determining a DOC removal rate according to a first embodiment. FIG. [Figure 7] FIG. 4 is a graph showing the relationship between Q / V and the DOC removal rate according to the first embodiment. [Figure 8] FIG. 4 is a diagram showing the relationship between the mixing time of wastewater and altered precipitates and the amount of precipitates in the first embodiment. [Figure 9] 2 is a schematic configuration diagram showing an example of a precipitate transformation section according to the first embodiment. FIG. [Figure 10] 2 is a schematic configuration diagram showing an example of a precipitate transformation section according to the first embodiment. FIG. [Figure 11] 2 is a schematic configuration diagram showing an example of a precipitate transformation section according to the first embodiment. FIG. [Figure 12] FIG. 11 is a schematic configuration diagram of a water treatment device according to a second embodiment. [Figure 13] FIG. 11 is a schematic configuration diagram of a water treatment device according to a second embodiment. [Figure 14] FIG. 11 is a schematic configuration diagram of a water treatment device according to a third embodiment. [Figure 15] FIG. 11 is a schematic configuration diagram of a water treatment device according to a fourth embodiment. [Figure 16] FIG. 11 is a schematic configuration diagram of a water treatment device according to a fifth embodiment. [Figure 17] FIG. 13 is a schematic configuration diagram of a water treatment system according to a sixth embodiment. [Figure 18] 13 is a flowchart showing a process flow executed by a water treatment device according to a seventh embodiment. [Figure 19] 13 is a flowchart showing a process flow executed by a water treatment device according to a seventh embodiment. [Figure 20] FIG. 13 is a schematic configuration diagram showing an example of a processing circuit that realizes each function of a water treatment device according to a seventh embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The following description of the embodiments will be given with reference to the accompanying drawings, in which the same contents and corresponding parts are designated by the same reference numerals, and detailed description thereof will be omitted.

[0012] Embodiment 1 FIG. 1 is a schematic diagram of a water treatment device 10 according to a first embodiment. The water treatment device 10 includes a first separation tank 1 that receives wastewater 11 and separates it into a first effluent 16 and a first precipitate 15, a reaction tank 2 that receives the first effluent 16 and brings the first effluent 16 into contact with a microorganism aggregate (floc) to cause a reaction, a second separation tank 3 that receives reacted water 17 from the reaction tank 2 and separates the reacted water 17 into a second effluent and a second precipitate 12, and a first separation tank 1 that takes at least a part of the second precipitate 12 into a precipitate transformation unit 4, transforms the second precipitate 12 to generate a transformed precipitate 14, and returns the transformed precipitate 14 to the first separation tank 1 or an upstream of the first separation tank 1 to mix with the wastewater 11 to increase the amount of the first precipitate 15. Here, a part of the second precipitate 12 is returned to the reaction tank 2. The second separation tank 3 may include a facility using a membrane, and may also include a facility in which the membrane is integrated with the reaction tank 2.

[0013] As shown in FIG. 2, the second precipitate 12 is formed by the aggregation of many flocs 151, which are aggregates of microorganisms. Furthermore, the flocs 151 are an aggregation of floc constituent units 152. The precipitate transformation unit 4 transforms the state of the flocs 151 in the second precipitate 12 to generate modified flocs 141. The modified flocs 141 are similarly an aggregation of modified floc constituent units 142. A large number of modified flocs 141 aggregate to form the modified precipitate 14. For example, the modified flocs 141 are formed by crushing the flocs 151 into small lumps and dispersing them. The modified floc constituent units 142 may have the same properties as the floc constituent units 152, or may have different properties due to dissolution, decomposition, etc.

[0014] 3 is a diagram showing an image of the flocs 151 coming into contact with the wastewater 11 and the solid organic matter 111 and soluble organic matter 112 in the wastewater 11 being adsorbed onto the flocs 151. Since the flocs 151 are an aggregate of microorganisms, the microorganisms take in and adsorb the solid organic matter 111 and soluble organic matter 112. 4 is a diagram showing an image of the modified floc 141 coming into contact with the wastewater 11 and the solid organic matter 111 and soluble organic matter 112 in the wastewater 11 being adsorbed onto the modified floc 141. Similarly, since the modified floc 141 is an aggregate of microorganisms, the microorganisms take in and adsorb the solid organic matter 111 and soluble organic matter 112. The modified floc 141 has an increased surface area per unit volume, for example, by being crushed, compared to unmodified floc 151, and can therefore take in and adsorb more of the solid organic matter 111 and soluble organic matter 112 in the wastewater 11.

[0015] The modified floc 141 may be a floc 151 with a complicated surface shape. By making the floc finer or making the surface shape more complicated, the surface area per unit volume of the floc can be increased, and the amount of organic matter taken up by microorganisms and the amount of organic matter adsorbed by microorganisms can be increased, so that the modified floc 141 can contain more solid organic matter 111 and dissolved organic matter 112. The thus modified precipitate 14 can contain more solid organic matter 111 and soluble organic matter 112 than the second precipitate 12 in the first separation tank 1, and therefore more organic matter can be precipitated as the first precipitate 15. Furthermore, when a coagulant, as described below, is added to the wastewater 11, the solid organic matter 111 and soluble organic matter 112 that could not be absorbed or adsorbed by the altered precipitate 14 can be coagulated and precipitated, and even more solid organic matter 111 and soluble organic matter 112 can be contained in the first precipitate 15 in the first separation tank 1. Furthermore, the solid organic matter 111 and the soluble organic matter 112 in the first effluent 16 separated in the first separation tank 1 are reduced by the uptake and adsorption of the solid organic matter 111 and the soluble organic matter 112 into the modified floc 141. When the solid organic matter 111 and the soluble organic matter 112 in the first effluent 16 are reduced, the amount of aeration required to remove these organic matters by biological treatment in the reaction tank 2 can be reduced, making it possible to save energy in the water treatment system.

[0016] Since the amount of organic matter contained in the flocs 151 can be increased by increasing the surface area per unit volume of the flocs 151, the generation of the modified flocs 141 can be achieved not only by the process of crushing the flocs 151 but also by the decomposition and dissolution processes. That is, the precipitate transformation unit 4 has the function of increasing the surface area per unit volume by making the flocs 151 in the second precipitate 12 finer or more complex in shape, and performs at least one of the processes of crushing, dissolving, and decomposing the flocs 151 in the second precipitate 12 in the precipitate transformation unit 4. Here, the process may be one of the crushing, decomposition, and dissolution, or a combination of two or more of them.

[0017] As the precipitate transformation unit 4 for crushing the flocs 151, for example, an apparatus configured as shown in FIG. 5 is considered. In this precipitate transformation unit 4, a circulation circuit 47 is formed in which the second precipitate 12 in the vessel 13 to which the second precipitate 12 has been sent is taken in by a pump 41 and returned to the vessel 13. The second precipitate 12 is sent out to the circulation circuit 47 by applying pressure to an absorber 43 by the pump 41, and passes through the absorber 43 having an inner diameter smaller than that of the circulation circuit. The absorber 43 is provided with an inlet 42 through which gas or liquid can be introduced. This generates a negative pressure in the absorber 43, which causes the gas or liquid to be sucked in from the inlet 42, thereby crushing the flocs 151 in the second precipitate 12. The magnitude of the negative pressure in the absorber 43 in the circulation circuit can be adjusted by the inner diameter of the absorber 43. The smaller the inner diameter of the absorber 43 is relative to the inner diameter of the circulation circuit 47, the greater the negative pressure becomes, and the more gas or liquid can be sucked in, resulting in a greater crushing effect. In the absorber 43, the sucked gas or liquid is mixed with the flocs 151 in the second precipitate 12. Since the inner diameter gradually increases toward the circulation circuit 47 connected to the downstream side of the absorber 43, the pressure changes from negative to positive, and at that time, the flocs 151 and the sucked gas or liquid are agitated by the pressure change, and the flocs 151 are crushed to become metamorphosed flocs 141.

[0018] That is, the apparatus may be configured to generate a negative pressure in the circulated second precipitate 12 to introduce at least one of gas and liquid. In the apparatus configured in this manner, the flocs 151 in the vessel 13 are crushed to become fine flocs or metamorphosed flocs 141 having complex shapes. Since the negative pressure generated in the absorber 43 is utilized, the gas or liquid to be sucked in is sucked into the absorber 43 without pressure, but the gas or liquid may be pressurized and fed into the absorber 43. The gas to be introduced is, for example, air, ozone, a mixture of air and ozone, etc. The liquid is, for example, an alkaline solution such as sodium hydroxide, or an acid solution such as sulfuric acid. When mixing gas and liquid, it is preferable to have a larger flow rate ratio G(Gas) / L(Liquid) of the gas and liquid, since this increases the stirring force and increases the effect of crushing the flocs. The amount of the second precipitate 12 in the vessel 13 can be monitored by installing a water level gauge or the like in the vessel 13.

[0019] In order to obtain the optimal Q / V value when the circulation flow rate of the second precipitate 12 is Q and the input amount is V, the relationship between the Q / V value and the DOC (dissolved organic matter) removal rate when the modified precipitate 14 obtained by treating the second precipitate 12 is mixed with the wastewater 11 was examined using the equipment shown in FIG. 6. For example, Q / V=10 means that 10 times the amount of the input second precipitate 12 is circulated. The DOC removal rate here is the ratio of the difference in DOC in the wastewater 11 before and after the modified precipitate 14 is input to the wastewater 11, to the DOC before the modified precipitate 14 is input to the wastewater 11. An ejector is used as the absorber 43 to suck in air, and negative pressure is generated in the circulation circuit 47 to crush the flocs 151 of the second precipitate 12 to generate the modified flocs 141. The modified precipitate 14 and air bubbles 18 are present in the container 13. The altered sediment 14 removed from the container 13 was mixed with the wastewater 11, and the concentration of the dissolved organic matter 112 was measured with a concentration meter 133 to determine the DOC removal rate.

[0020] As shown in Fig. 7, the larger the Q / V value, that is, the larger the circulation flow rate Q is relative to the input amount V, the higher the DOC removal rate, and at Q / V = 120 the DOC removal rate remained roughly constant. Therefore, a Q / V value of 10 or more is preferable. Also, since the larger the Q / V value, the more time and power are required to generate the metamorphic flocs 141, a Q / V value of 120 or less is preferable. Furthermore, from the viewpoint of shortening the treatment time and saving energy, a Q / V value of 10 or more and 60 or less, more preferably 10 or more and 40 or less, is preferable, and a sufficient DOC removal rate of 7% to 15% is obtained. When the altered precipitate 14 containing the altered floc 141 thus produced is mixed with the wastewater 11, 1 m3 The amount of metamorphic sediment per unit is 0.01kg-DS(Dried Sludge) / m 3 More than 0.5kgDS / m 3 By setting the concentration to less than 0.01 kg-DS / m, the amount of the first precipitate 15 could be effectively increased. 3 If it is smaller than this, sufficient DOC removal rate cannot be obtained, and it is 0.5 kg-DS / m 3 If it is larger than this, the recovery of the first precipitate 15 in the first separation tank 1 becomes insufficient, and a part of the metamorphic precipitate 14 containing the solid organic matter 111 and the soluble organic matter 112 in the wastewater 11 is contained in the first effluent 16 and flows into the reaction tank 2. More preferably, it is 0.05 kg-DS / m 3 More than 0.15kg-DS / m 3 It is better to use the following:

[0021] The mixing time of the wastewater 11 and the modified precipitate 14 may be extended to allow the modified floc 141 to incorporate or adsorb the solid organic matter 111 and the soluble organic matter 112, thereby increasing the effect of containing the solid organic matter 111 and the soluble organic matter 112 in the modified precipitate 14. FIG. 8 is a diagram showing the relationship between the mixing time of the wastewater 11 and the modified precipitate 14 and the amount of precipitate of the first precipitate 15 (the conditions are the same as those in Table 1 described later). From this, the amount of precipitate cannot be increased until about 3 minutes after the modified precipitate 14 is mixed with the wastewater 11. This is because the time is short, so there is not enough opportunity for the modified precipitate 14 to come into contact with the solid organic matter 111 and the soluble organic matter 112, and the incorporation and adsorption of the solid organic matter 111 and the soluble organic matter 112 into the modified precipitate 14 is insufficient. In addition, the amount of precipitate of the first precipitate 15 increases rapidly from about 6 minutes. This is because the opportunity for the solid organic matter 111 and the soluble organic matter 112 in the wastewater 11 to come into contact with the modified floc 141 increases, and the incorporation and adsorption of the solid organic matter 111 and the soluble organic matter 112 into the modified floc 141 progresses. After that, the increase in the amount of precipitate gradually becomes slower. Therefore, it is preferable to set the mixing time of the modified precipitate 14 and the wastewater 11 to be longer than 5 minutes. In order to avoid excessively long mixing times, the mixing time is preferably 6 minutes or more and 20 minutes or less. By appropriately setting the Q / V value and the mixing time in this manner, the amount of first precipitate 15 separated in first separation tank 1 can be increased, and the recovery rate of the organic matter can be improved.

[0022] As an apparatus for generating the modified precipitate 14 including the modified flocs 141 in which the flocs 151 in the second precipitate 12 are finer or have a more complicated shape, there is, for example, a means for generating the modified precipitate 14 by heating or supplying an acid or alkaline solution as shown in FIG. 9. Heating or supplying an acid solution, or supplying an acid solution while heating. By heating or supplying an alkaline solution, or supplying an alkaline solution while heating, the flocs 151 in the second precipitate 12 can be dissolved or decomposed, or dissolved and decomposed, to thereby make the flocs 151 finer or to make the shape more complicated. The temperature during heating is, for example, 50° C. to 100° C. As the acid solution, sulfuric acid, hydrochloric acid, or the like can be used, and as the alkaline solution, an aqueous solution of sodium hydroxide, potassium hydroxide, or the like can be used. In this way, the modified precipitate 14 in which the state of the flocs 151 in the second precipitate 12 is modified may be generated. By mixing the modified precipitate 14 generated in this way with the wastewater 11, the amount of the first precipitate 15 can be increased.

[0023] Furthermore, as shown in Fig. 10, a gas 19 containing ozone may be supplied to the second precipitate 12 to dissolve or decompose the flocs 151 in the second precipitate 12, thereby generating modified flocs 141 which are finer or have a more complex shape. This makes it possible to dissolve or decompose the flocs 151 in the second precipitate 12, thereby making the flocs 151 finer or more complex in shape. This increases the surface area per unit volume of the flocs, thereby promoting the uptake and adsorption of the solid organic matter 111 and the soluble organic matter 112. That is, by supplying ozone to the second precipitate 12 to generate a modified precipitate 14 containing modified flocs 141 which are obtained by modifying the state of the flocs 151 in the second precipitate 12, the amount of the first precipitate 15 can be increased by mixing the modified precipitate 14 with the wastewater 11.

[0024] Also, in order to break down the flocs 151 in the second precipitate 12, an ultrasonic irradiator 44 can be used, for example, as shown in FIG. 11. For example, by irradiating the second precipitate 12 with ultrasonic waves in a pulsed manner, the flocs 151 are broken down and modified flocs 141 having finer or more complex shapes can be generated. This increases the surface area per unit volume of the flocs, and promotes the uptake and adsorption of the solid organic matter 111 and the soluble organic matter 112. That is, the state of the flocs 151 in the second precipitate 12 is altered by the ultrasonic irradiator 44 to generate modified precipitates 14, which are then mixed with the wastewater 11 to increase the amount of the first precipitate 15.

[0025] The modified precipitate 14 may be formed by combining two or more selected from the precipitate-modified portions 4 shown in Figs. 5 and 9 to 11 .

[0026] In this manner, the system includes a first separation tank 1 which receives the wastewater 11 and separates it into a first effluent 16 and a first precipitate 15, a reaction tank 2 which receives the first effluent 16 and brings the first effluent 16 into contact with microorganisms to cause a reaction, and a second separation tank 3 which receives the reacted water 17 from the reaction tank 2 and separates the reacted water 17 into a second effluent and a second precipitate 12. The system further includes a precipitate transformation unit 4 which takes in at least a portion of the second precipitate 12 and generates a modified precipitate 14 by transforming flocs 151 which are an aggregate of microorganisms contained in the second precipitate 12. By transferring the modified precipitate 14 to the first separation tank 1 or upstream of the first separation tank 1 and mixing it with the wastewater 11, the second precipitate 12 separated in the second separation tank 3 becomes the modified precipitate 14 in the precipitate transformation unit 4 and is mixed with the wastewater 11, so that a larger amount of the solid organic matter 111 and the soluble organic matter 112 contained in the wastewater 11 can be contained in the first precipitate 15.

[0027] In the first separation tank 1, a larger amount of organic matter can be precipitated as the first precipitate 15. The first precipitate 15 can be concentrated and digested to extract energy such as methane gas, and therefore an increase in the amount of the first precipitate 15 can increase the amount of energy recovered from the wastewater. Furthermore, if a portion of the excess sludge is converted into the modified precipitate 14 instead of being extracted from the water treatment device 10 as the second precipitate 12, the amount of the second precipitate 12, which is difficult to digest, can be reduced. Furthermore, if the entire amount of the excess sludge is converted into the modified precipitate 14, a water treatment system 100 can be constructed that does not discharge the second precipitate 12. In addition, the amount of solid organic matter 111 and dissolved organic matter 112 present in the first effluent 16 separated in the first separation tank 1 can be reduced, and the amount of aeration required for biological treatment in the reaction tank 2 can be reduced, resulting in energy savings.

[0028] In addition, the precipitate transformation section 4 increases the surface area per unit volume by finely dividing or by making the shape of the flocs 151 in the second precipitate 12 more complex, so that the transformed precipitate 14 produced can contain more of the solid organic matter 111 and soluble organic matter 112 in the wastewater 11. Furthermore, in the precipitate transformation section 4, by performing at least one of the processes of crushing, dissolving, and decomposing the flocs 151 in the second precipitate 12, it is possible to produce a transformed precipitate 14 in which the state of the flocs 151, which are aggregates of microorganisms in the second precipitate 12, is transformed. Furthermore, by generating a negative pressure in the circulated second precipitate 12 and introducing at least one of a gas and a liquid, it is possible to generate a modified precipitate 14 in which the state of the flocs 151, which are an aggregate of microorganisms in the second precipitate 12, has been modified. By supplying at least one of heat and an alkaline or acidic solution to the second precipitate 12 to dissolve the flocs 151 in the second precipitate 12, it is possible to generate a modified precipitate 14 in which the state of the flocs 151, which are an aggregate of microorganisms in the second precipitate 12, has been modified. By supplying ozone to the second precipitate 12 to decompose the flocs 151 in the second precipitate 12, it is possible to generate a modified precipitate 14 in which the state of the flocs 151, which are an aggregate of microorganisms in the second precipitate 12, has been modified. By irradiating the second precipitate 12 with ultrasonic waves to break down the flocs 151 in the second precipitate 12, it is possible to generate a modified precipitate 14 in which the state of the flocs 151, which are an aggregate of microorganisms in the second precipitate 12, has been modified.

[0029] By mixing the modified sediment 14 generated in the sediment transformation section 4 with the wastewater 11 in this manner, a larger amount of organic matter can be precipitated as the first sediment 15 in the first separation tank 1, thereby increasing the amount of recovered energy and reducing the amount of energy required for biological treatment in the reaction tank 2.

[0030] Embodiment 2 12 and 13 are schematic configuration diagrams of a water treatment device 10 according to embodiment 2. Water treatment device 10 according to embodiment 2 differs from embodiment 1 in that it includes a flocculant addition section 5 that adds a flocculant to modified precipitate 14 returned from the sediment transformation section 4 to the first separation tank 1 or to the upstream of the first separation tank 1. The other configurations are the same as those of embodiment 1.

[0031] The water treatment device 10 shown in Fig. 12 includes a flocculant addition section 5 that adds a flocculant to a mixture of wastewater 11 and modified precipitate 14 returned from the sediment transformation section 4 to the upstream of the first separation tank 1. For example, polyaluminum chloride, aluminum sulfate, ferric chloride, polymer flocculant, etc. are used as the flocculant. As explained in the first embodiment with reference to Fig. 4, when the modified flocs 141 come into contact with the wastewater 11, the solid organic matter 111 and the soluble organic matter 112 in the wastewater 11 are adsorbed to the modified flocs 141. If a flocculant is added when the wastewater 11 and the modified precipitate 14 are mixed, the solid organic matter 111 and the soluble organic matter 112 that are not adsorbed to the modified precipitate 14 are easily coagulated and precipitated, and in addition to the effects described in the first embodiment, the amount of the first precipitate 15 can be further increased. In addition, the Al contained in the flocculant 3+ , Fe 3+ Since these cations form insoluble salts with phosphorus, the phosphorus contained in the wastewater 11 can be removed by precipitation.

[0032] When a metal-based flocculant is used as the flocculant, the flocculant addition rate is preferably 0.05 mg-ME / mg-SS or more and 0.25 mg-ME / mg-SS or less per unit weight of SS (suspended solids) of the altered precipitate 14 added to the wastewater 11. The metal used in the flocculant is expressed as ME. It may also be expressed as the SS of the second precipitate 12. This is because it has been confirmed that there is no significant difference between the SS of the second precipitate 12 and the altered precipitate 14. When the flocculant addition rate is less than 0.05 mg-ME / mg-SS, the amount of flocculant is small and there is no effect of further increasing the amount of the first precipitate 15. When the flocculant addition rate is more than 0.25 mg-ME / mg-SS, the amount of the first precipitate 15 increases, but the cost of the flocculant becomes too high. In addition, iron, aluminum, etc. are used as the metal. Furthermore, when a polymer organic flocculant is used as the flocculant, the flocculant addition rate is preferably 0.001 mg / mg-SS or more and 0.007 mg / mg-SS or less per unit weight of the altered precipitate 14 added to the wastewater 11. If the flocculant addition rate is less than 0.001 mg / mg-SS, the amount of flocculant added is small and the effect of further increasing the amount of the first precipitate 15 is not obtained. If the flocculant addition rate is more than 0.007 mg / mg-SS, the amount of the first precipitate 15 increases, but the cost of the flocculant becomes too high.

[0033] As described above, the flocculant is preferably added based on the amount of the modified precipitate 14 transferred to the first separation tank 1 or its upstream. For example, the flocculant adding unit 5 of the water treatment device 10 shown in FIG. 13 is composed of a flocculant storage unit 51, an adding unit 52, and a flocculant addition amount control unit 53, and calculates the supply amount of flocculant based on the measured values ​​of the solid concentration (hereinafter also simply called the concentration) of the modified precipitate 14 and the flow rate, and adds the flocculant based on the calculated supply amount. For example, the measured values ​​are obtained from the concentration of the modified precipitate 14 transferred from the sediment transformation unit 4 and the operating state of the modified precipitate water conveying device 45 such as a pump, and the amount of flocculant required is calculated based on the measured values ​​by the flocculant addition amount control unit 53. Then, the flocculant is added in the adding unit 52 based on the amount of flocculant supplied calculated and controlled by the flocculant addition amount control unit 53. In addition, the concentration of the transformed precipitate 14 may be measured using a concentration meter 63 shown in Figure 14 described below, or a concentration meter (not shown) installed in the precipitate transformation section 4, in the piping connecting the precipitate transformation section 4 and the wastewater 14, etc. may also be used. Since the amount of solids in the altered precipitate 14 is determined by multiplying the concentration by the flow rate, the amount of flocculant required can be calculated by the flocculant addition amount control unit 53, and the amount added can be adjusted by controlling the addition unit 52. By adding the flocculant in this manner, the flocculant can be used without excess or deficiency.

[0034] For example, if the amount of the altered sediment 14 added to the wastewater 11 is 0.5 kg-sludge DS / m 3 In this case, it is preferable to use FeCl3 as a flocculant and set the amount of the altered precipitate 14 to 0.05 to 0.25 mg-Fe / mg-SS (SS is the altered precipitate). Using FeCl3 as a coagulant, a jar test was conducted in which the coagulant, metamorphic sediment 14, and wastewater 11 were mixed at Q / V=30. The results showed that SS removal from the first effluent 16 was effective at 0.05 mg-Fe / mg-SS or more, and that the organic matter removal effect in the wastewater 11 was greatest at 0.1-0.2 mg-Fe / mg-SS. Furthermore, when the coagulant was a polymer coagulant, the organic matter removal effect in the wastewater 11 was greatest at 0.002-0.005 mg / mg-SS. From the above, it was possible to increase the amount of first sediment by approximately 20% compared to when no coagulant was added.

[0035] The flocculant storage section 51 and the addition section 52 may be provided before the altered precipitate 14 is mixed with the wastewater 11, or may be provided so that the flocculant is added during mixing. The set values, the calculation formula, etc. may be stored in advance in the flocculant addition amount control unit 53, or an input unit may be provided that allows the operator of the water treatment device 10 to input them.

[0036] In this way, the system is provided with a flocculant adding section 5 that adds a flocculant to the altered precipitate 14 or the mixture of the altered precipitate 14 and wastewater 11 that is returned from the precipitate transformation section 4 to the upstream of the first separation tank 1, and by adding the flocculant, the solid organic matter 111 and the soluble organic matter 112 in the wastewater 11 can be flocculated to further increase the amount of the first precipitate 15. In addition, by flocculating phosphorus with the metal ions contained in the flocculant to form an insoluble salt and precipitating it in the first separation tank 1, the phosphorus concentration in the first effluent water 16 can be reduced and the water quality can be improved. In addition, the concentration and flow rate of the modified precipitate 14 sent from the precipitate transformation section 4 are measured, the amount of flocculant to be supplied is calculated based on the measured values, and the appropriate amount of flocculant can be added by adding the flocculant based on the amount supplied.

[0037] In the first embodiment, the relationship between the mixing time of the wastewater 11 and the modified precipitate 14 and the amount of precipitate of the first precipitate 15 was shown using Fig. 8, but similar results were obtained when a flocculant was added. That is, it is preferable to set the mixing time of the modified precipitate 14 and the wastewater 11 after adding a flocculant to be longer than 5 minutes. Furthermore, since the amount of precipitate does not increase significantly even if the mixing time is increased, the mixing time is preferably 6 minutes or more and 20 minutes or less so as not to become too long.

[0038] Embodiment 3 Fig. 14 is a schematic configuration diagram of a water treatment device 10 according to embodiment 3. Water treatment device 10 according to embodiment 3 differs from embodiments 1 and 2 in that it includes a second precipitate amount control unit 6 that controls the amount of the second precipitate transferred from the second separation tank 3 to the precipitate transformation unit 4. The other configurations are the same as those of embodiment 1 or 2.

[0039] The water treatment device 10 shown in FIG. 14 separates the reaction water 17 into the second effluent water and the second precipitate 12 in the second separation tank 3. Then, a part of the second precipitate 12 is returned to the reaction tank 2, and the remaining second precipitate 12 is transferred to the precipitate transformation unit 4. The second precipitate amount control unit 6 calculates the amount of the second precipitate 12 from the concentration and flow rate values ​​measured using a concentration meter 63 that measures the solid concentration contained in the second precipitate 12 and a flow meter 62 that measures the flow rate of the second precipitate 12. The amount of the second precipitate 12 transferred to the precipitate transformation unit 4 is controlled by controlling the opening and closing degree of the valve 61 so that the microbial concentration in the reaction tank 2 can be maintained at a predetermined value. At that time, the entire remaining amount except the amount of the second precipitate 12 transferred to the reaction tank 2 may be transferred to the precipitate transformation unit 4, or a part of the second precipitate 12 may be transferred to the precipitate transformation unit 4 and the remainder may be transferred to the concentration and digestion process. The second precipitate 12 is mainly composed of microorganisms in the reaction tank 2, i.e., activated sludge, and is less likely to generate digestion gas than the first precipitate 15 contained in the wastewater 11. Therefore, it is preferable to increase the amount of first precipitate 15 separated in the first separation tank 1 rather than the second precipitate 12 separated in the second separation tank 3 as the precipitate to be recovered in order to generate digestion gas in the digestion process and use it as energy.

[0040] Therefore, the second precipitate amount control unit 6 controls the amount of the second precipitate 12 so as to transfer all or a part of the remaining amount excluding the amount of the second precipitate 12 required to maintain the microbial concentration in the reaction tank 2 at a predetermined value to the precipitate transformation unit 4. The predetermined microbial concentration maintained in the reaction tank 2 is a value that is preset when operating the water treatment device 10. By maintaining the microbial concentration in the reaction tank 2 at a predetermined value, the water treatment device 10 can be operated stably, while the modified precipitate 14 obtained by modifying the second precipitate 12 is returned to the first separation tank 1 or upstream of the first separation tank 1, so that the modified floc 141 in the modified precipitate 14 contains more of the solid organic matter 111 and soluble organic matter 112 contained in the wastewater 11, thereby improving the recovery rate of organic matter by the first precipitate 15 separated in the first separation tank 1.

[0041] The transfer of the second precipitate 12 from the second separation tank 3 to the precipitate transformation unit 4 may be performed intermittently in accordance with the timing of the withdrawal of excess sludge from the water treatment device 10, or the transfer of the modified precipitate 14 from the precipitate transformation unit 4 to the first separation tank 1 may be performed continuously. In either case, it is preferable to continuously transfer the modified precipitate 14 from the precipitate transformation unit 4 to the first separation tank 1 or upstream of the first separation tank 1. This makes it possible to stably increase the amount of the first precipitate 15 in the first separation tank 1 in response to the continuously flowing in wastewater 11.

[0042] The formulas for calculating the predetermined microbial concentration to be maintained in the reaction tank 2, the set values ​​of each value measured by the concentration meter 63 and the flow meter 62, the amount of the second precipitate 12 to be transferred to the precipitate transformation section 4, etc. may be stored in advance in the second precipitate amount control section 6, or an input section may be provided that allows the operator of the water treatment device 10 to input the formulas.

[0043] Embodiment 4 Fig. 15 is a schematic configuration diagram of a water treatment device 10 according to embodiment 4. The water treatment device 10 according to embodiment 4 differs from embodiments 1 to 3 in that it includes a metamorphic precipitate control unit 7 that grasps the state of wastewater 11. The other configurations are the same as those of embodiments 1 to 3. In the water treatment device 10 shown in Fig. 15, the organic component concentration of the wastewater 11 measured by the concentration meter 73, the flow rate of the first effluent 16 measured by the flow meter 72, and the solid concentration of the second precipitate 12 measured by the concentration meter 63 are sent to the modified precipitate control unit 7 to grasp the respective states, and the modified precipitate control unit 7 determines the conditions for modifying the modified precipitate 14 generated in the precipitate modification unit from the respective measurement values ​​acquired, and transmits them to the precipitate modification unit 4. The precipitate modification unit 4 generates the modified precipitate 14 according to the conditions transmitted from the modified precipitate control unit 7, and transfers it to the first separation tank 1 or its upstream. Here, the conditions for generating the modified precipitate 14 are numerical conditions according to the various configurations of the precipitate modification unit 4 described in the first embodiment.

[0044] In this way, by providing a modified sediment control unit 7 that grasps the states of the wastewater 11 and the second sediment 12 based on the measured values ​​of the organic component concentration of the wastewater 11, the flow rate of the first effluent 16, and the solids concentration of the second sediment 12, and determines the conditions for generating a modified sediment 14 to be transferred to the first separation tank 1 or upstream of the first separation tank 1 based on these values, it is possible to generate a modified sediment 14 with appropriate properties in response to fluctuations in the temporal flow rate of the wastewater 11, the organic component concentration, the solids concentration of the second sediment 12, etc.

[0045] The modified precipitate control unit 7 can determine the conditions for generating the modified precipitate 14, such as the equipment, Q / V, gas to be introduced, and solution. The modified precipitate control unit 7 can also grasp the amount of the second precipitate 12 stored in the precipitate transformation unit 4, and can use that amount to determine the conditions for generating an appropriate modified precipitate 14. Data on the equipment installed in advance for generating the modified precipitate 14 may be stored and called up from the modified precipitate control unit 7 as appropriate. The function of the modified precipitate control unit 7 may be integrated into the sediment transformation unit 4, and the sediment transformation unit 4 may perform the judgment and calculation. In this embodiment, the flow rate of the first effluent 16 is measured, but the flow rate of the wastewater 11 flowing into the first separation tank 1 may be measured directly.

[0046] Embodiment 5. Fig. 16 is a schematic configuration diagram of a water treatment device 10 according to embodiment 5. The water treatment device 10 according to embodiment 5 is the same as embodiment 4 in that it includes a modified precipitate control unit 7 that grasps the state of wastewater 11, but differs in that it can control the amount of modified precipitate 14 transferred to wastewater 11. The other configurations are the same as those of embodiments 1 to 4.

[0047] As described above, by mixing the modified precipitate 14 with the wastewater 11, a larger amount of the organic matter contained in the wastewater 11 can be incorporated into the modified precipitate 14, and the recovery rate of the organic matter by the first precipitate 15 separated in the first separation tank 1 can be improved. However, since the concentration and flow rate of the organic components in the wastewater 11 fluctuate from moment to moment, it is necessary to transport an appropriate amount of modified precipitate 14 accordingly.

[0048] Therefore, the water treatment device 10 of this embodiment is provided with a modified precipitate control unit 7 that grasps the state of the wastewater 11 and controls the supply amount of the modified precipitate 14 to be transferred to the first separation tank 1 or its upstream. In the water treatment device 10 shown in Fig. 16, the organic component concentration of the wastewater 11 measured by the concentration meter 73, the flow rate of the first effluent 16 measured by the flowmeter 72, and the solid concentration of the second precipitate 12 measured by the concentration meter 63 are sent to the modified precipitate control unit 7 to grasp the respective states, and the amount of modified precipitate 14 to be mixed into the wastewater 11 is calculated from the respective measurement values ​​acquired by the modified precipitate control unit 7. Next, the calculated amount of modified precipitate 14 is sent to the modified precipitate water supply device 45. The modified precipitate water supply device 45 transfers the transmitted amount of modified precipitate 14 to the first separation tank 1 or its upstream. In place of the concentration meter 63, a concentration meter (not shown) installed in the sediment transformation unit 4 or in a pipe connecting the sediment transformation unit 4 and the wastewater 14 may be used.

[0049] In this way, the modified precipitate control unit 7 is provided which grasps the state of the wastewater 11 based on the organic component concentration and flow rate of the wastewater 11, and calculates the amount of modified precipitate 14 to be transferred to the first separation tank 1 or the upstream of the first separation tank 1 based on the solid concentration of the second precipitate 12 or the modified precipitate 14, and transfers the modified precipitate 14 to the first separation tank 1 or the upstream of the first separation tank 1 based on the calculation result, thereby making it possible to transfer an appropriate amount of modified precipitate 14 without excess or deficiency in response to the moment-to-moment fluctuations in the concentration and flow rate of the organic components in the wastewater 11. As a result, the amount of the first precipitate 15 in the first separation tank 1 can be stably increased in response to the moment-to-moment fluctuations in the wastewater 11. Although the flow rate of first effluent water 16 is measured in this embodiment, the flow rate of wastewater 11 flowing into first separation tank 1 may be measured directly.

[0050] Embodiment 6 17 is a schematic configuration diagram of a water treatment system 100 according to embodiment 6. The water treatment system 100 according to embodiment 6 includes the water treatment device 10 described in any of embodiments 1 to 5. As shown in FIG. 17, the water treatment system 100 includes the water treatment device 10 shown in FIG. 1, a first concentrator 20 for concentrating a precipitate including the first precipitate 15 transferred from the water treatment device 10 to form concentrated sludge, a second concentrator 21 for concentrating a precipitate including the second precipitate 12 to form concentrated sludge, and a digester 30 for mixing and heating the concentrated sludge to decompose organic matter in the concentrated sludge and generate digestion gas. The water treatment device 10 may have any of the configurations described in the first to fifth embodiments. In addition, when the second precipitate 12 is entirely transferred to the precipitate transformation section 4, the second concentrator 21 may not be used. That is, the concentrator may include at least the first concentrator 20, and may include the first concentrator 20 and the second concentrator 21.

[0051] In this way, the water treatment system 100 comprises a water treatment device 10 according to the present disclosure, a concentration device that concentrates a precipitate containing at least a first precipitate 15 transferred from the water treatment device 10 to form concentrated sludge, and a digester 30 that heats the concentrated sludge to decompose organic matter contained in the concentrated sludge and generate digestion gas. By returning the modified precipitate 14 obtained by transforming the second precipitate 12 to the first separation tank 1 or upstream of the first separation tank 1, the recovery rate of organic matter by the first precipitate 15 separated in the first separation tank 1 can be improved, and more digestion gas can be generated and utilized as carbon-neutral energy.

[0052] Note that it is also possible to operate the water treatment device 10 by combining any two or all of the third to fifth embodiments, thereby making it possible to recover a larger amount of organic matter as the first precipitate 15. Furthermore, by combining any two or all of the first to fifth embodiments, it is possible to recover an even larger amount of organic matter as the first precipitate 15.

[0053] Embodiment 7 FIG. 18 shows a flow chart of the treatment flow executed by the water treatment device 10. First, wastewater 11 is received and separated into a first effluent 16 and a first precipitate 15 (first separation step S101). Then, the first effluent 16 is received and the first effluent 16 is brought into contact with microorganisms to react (reaction step S102). Then, the reacted water 17 obtained in the reaction step is received and separated into a second effluent and a second precipitate 12 (second separation step S103). Then, at least a part of the second precipitate 12 is taken in, and the state of the flocs 151, which are an aggregate of microorganisms in the second precipitate 12, is altered to generate an altered precipitate 14 (precipitate alteration step S104). Furthermore, the altered precipitate 14 thus generated is mixed with wastewater 11, and organic matter in the wastewater 11 is taken in and precipitated (mixing step S105).

[0054] In this manner, wastewater 11 is received and separated into first effluent 16 and first precipitate 15, the first effluent 16 is received, the first effluent 16 is brought into contact with microorganisms to cause a reaction, the reacted water 17 is separated into second effluent and second precipitate 12, the state of flocs 151, which are an aggregate of microorganisms contained in the second precipitate 12, is altered to produce altered precipitate 14, the altered precipitate 14 is mixed with wastewater 11, and organic matter in wastewater 11 is taken up and precipitated. This makes it possible to contain a larger amount of organic matter contained in wastewater 11 in altered precipitate 14, thereby increasing the amount of first precipitate 15 separated in first separation tank 1 and improving the recovery rate of organic matter.

[0055] Fig. 19 is a flowchart showing a treatment flow executed by a water treatment device 10 including a flocculant addition unit 5 that adds a flocculant as described in the second embodiment. The first separation step S101, reaction step S102, second separation step S103, precipitate transformation step S104, and mixing step S105 are the same as those described above, and include a flocculant addition step S106 in which a flocculant is added to a mixture of the transformed precipitate 14 and wastewater 11, and organic matter in the wastewater 11 is captured and precipitated. A flocculant addition step of adding a flocculant to the transformed precipitate 14 may be provided before the mixing step S105. By adding a flocculant to the modified precipitate 14 or a mixture of the modified precipitate 14 and wastewater 11, and trapping and precipitating the organic matter in the wastewater 11, the amount of the first precipitate 15 separated in the first separation tank 1 can be further increased, thereby further improving the recovery rate of the organic matter.

[0056] Here, each function of the water treatment device 10 is realized by a processing circuit. Fig. 20 is a schematic configuration diagram showing an example of a processing circuit that realizes each function of the water treatment device 10. The water treatment device 10 has a processor 90, a storage device 91, a communication I / F (interface) 92, etc. For example, a CPU (Central Processing Unit) is used as the processor 90. The storage device 91 transmits and receives data to and from the processor 90 and stores the data. Measurement data from the flowmeters 62, 72, concentration meters 63, 73, etc. are acquired by the flocculant addition amount control unit 51, the second precipitate amount control unit 6, the altered precipitate control unit 7, etc. of the water treatment device 10 via the communication I / F 92. Calculations and judgments performed by the flocculant addition amount control unit 53, the second precipitate amount control unit 6, the altered precipitate control unit 7, etc. are executed by a processor 90. The acquired measurement data, arithmetic expressions, etc. are stored in a storage device 91.

[0057] The processor 90 and the storage device 91 may be one shared device or a plurality of devices may be provided. The processor 90 may include, for example, an application specific integrated circuit (ASIC), an integrated circuit (IC), a digital signal processor (DSP), a field programmable gate array (FPGA), or other logic circuitry, and various signal processing circuits. A plurality of processors 90, either of the same type or of different types, may be provided, so that each process is shared and executed by a plurality of arithmetic processing devices.

[0058] The multiple storage devices 91 include, for example, a RAM (Random Access Memory) configured to enable data to be read from and written to by the processor 90, a ROM (Read Only Memory) configured to enable data to be read from the processor 90, a hard disk, etc.

[0059] Each function of the water treatment device 10 is realized by a processor 90 executing software or a program stored in a storage device 91 and cooperating with hardware. Setting data to be set in the water treatment device 10 may be stored in the storage device 91 as part of the software or program, or may be input by the operator of the water treatment device 10. A non-transitory recording medium 911 on which a water treatment program 912 is recorded may be distributed and installed in the storage device 91 of the water treatment device 10.

[0060] The effects of the present disclosure will be described in comparison with specific examples of the present disclosure and comparative examples. Example 1. Using the water treatment device 10 shown in Figure 1 described in embodiment 1 and the precipitate transformation unit 4 shown in Figure 5, a transformed precipitate 14 was generated, and the transformed precipitate 14 was returned upstream of the first separation tank 1 and mixed with the wastewater 11. 150 L / d of wastewater containing organic matter was treated as raw water. The DOC of wastewater 11 was 30 mg / L, and the SS (suspended solids) was 130 mg / L. The mixing ratio of altered sediment 14 to wastewater 11 was 0.1 kg-sludge DS / m 3 The modified precipitate 14 was added and mixed upstream of the first separation tank 1 by the precipitate transformation unit 4 so that the first precipitate 15 and the second precipitate 12 were concentrated, and methane gas was extracted using an anaerobic digester. Furthermore, in the precipitate transformation unit 4, negative pressure was generated in the absorber 43 installed in the circulation circuit 47, and air was sucked in from the inlet 42. As a result, the flocs 151 in the second precipitate 12 were crushed and transformed to generate the modified precipitate 14. The modified precipitate 14 was returned to the first separation tank 1 and mixed with the wastewater 11 for 6 minutes, and then the DOC in the first effluent 16 was measured to determine the DOC removal rate. At this time, Q / V was set to 30.

[0061] Example 2. Using the water treatment device 10 shown in FIG. 12 and described in the second embodiment, the altered precipitate 14 was returned to the upstream of the first separation tank 1 and mixed with the wastewater 11. A flocculant was also added and mixed. Ferric chloride FeCl3 was used as the flocculant, and the flocculant addition rate was 0.1 mg-Fe / mg-SS. The other conditions were the same as in Example 1.

[0062] Comparative Example 1 1 described in the first embodiment was used, the sediment transformation unit 4 was not used, and the second sediment 12 was not returned to the upstream of the first separation tank 1 for mixing. The other conditions were the same as those in the first embodiment.

[0063] Comparative Example 2 1 described in the first embodiment, the second precipitate 12 was returned directly to the upstream of the first separation tank 1 without using the precipitate converter 4 and mixed with the wastewater 11. The other conditions were the same as those in the first embodiment.

[0064] Table 1 shows the measurement results of each item in Examples 1 and 2 and Comparative Examples 1 and 2. From these results, the amount of precipitate in Example 1 was 3.8 times (=190÷50) that of Comparative Example 1 and 1.1 times (=190÷170) that of Comparative Example 2, and the amount of precipitate in Example 2 was 4.5 times (=190÷50) that of Comparative Example 1 and 1.3 times (=190÷50) that of Comparative Example 2. The reduction rate of DOC in the first effluent 16 compared to Comparative Example 1 was 20% (=(30-24)÷30×100) in Example 1, 33% (=(30-20)÷30×100) in Example 2, 3% (=(30-29)÷30×100) in Comparative Example 1, and 7% (=(30-28)÷30×100) in Comparative Example 2. The reduction rate of SS in the first effluent 16 was 48% (=(130-68)÷130×100) in Example 1, 54% (=(130-60)÷130×100) in Example 2, and 38% (=(130-80)÷130×100) in Comparative Examples 1 and 2. From the above, it was confirmed that the effects of the Examples were greater than those of the Comparative Examples. As a result, the aeration air volume required in the reaction tank 2 was reduced by 7% in Example 1 and by 10% in Example 2 compared to Comparative Example 1. The amount of methane gas generated was increased by 40% in Example 1 and 60% in Example 2 compared to Comparative Example 2. This is believed to be due to the fact that the amount of the first precipitate 15 was increased by mixing the metamorphic precipitate 14 with the wastewater 11, and also due to the fact that the amount of SS and organic matter in the first effluent water 16 was reduced.

[0065] [Table 1]

[0066] Furthermore, in the water treatment device 10 and water treatment system 100 according to the present disclosure, since there is a water flow of the wastewater 11, a mixing device for mixing the wastewater 11 and the metamorphic precipitate 14 is not required, but if there is sufficient space, etc., a mixing device may be used for mixing.

[0067] In the present disclosure, various exemplary embodiments are described, but various features, aspects, and functions described in one or more embodiments are not limited to the application of a specific embodiment, and can be applied to the embodiments alone or in various combinations. Therefore, countless modifications not illustrated are expected within the scope of the technology disclosed in the present specification. For example, the modification, addition, or omission of at least one component, and the extraction and combination of at least one component with components of other embodiments are included. [Explanation of symbols]

[0068] 1 first separation tank, 2 reaction tank, 3 second separation tank, 4 sediment transformation section, 5 coagulant addition section, 6 second sediment amount control section, 7 modified sediment control section, 10 water treatment device, 11 wastewater, 12 second sediment, 13 container, 14 modified sediment, 15 first sediment, 16 first effluent, 17 reaction water, 20 first concentration device, 21 second concentration device, 30 digester, 41 pump, 42 inlet, 43 absorption device, 44 ultrasonic irradiator, 45 modified sediment water conveying device, 47 circulation circuit, 52 addition section, 53 coagulant addition amount control section, 61 valve, 62, 72 flow meter, 63, 73 concentration meter, 100 water treatment system, 111 solid organic matter, 112 soluble organic matter, 141 modified floc, 142 modified floc constituent unit, 151 Flock, 152 flock building blocks

Claims

1. A first separation tank that receives wastewater and separates it into first effluent and first sediment, A reaction tank that receives the first effluent and brings the first effluent into contact with microorganisms for a reaction, The system includes a second separation tank that receives reaction water from the reaction tank and separates the reaction water into second effluent and second precipitate, A water treatment apparatus further comprising a precipitate alteration unit that takes in at least a portion of the second precipitate and generates an altered precipitate in which the flocs, which are aggregates of microorganisms contained in the second precipitate, are altered, and the altered precipitate is transported to the first separation tank or upstream of the first separation tank and mixed with the wastewater, The water treatment apparatus is characterized in that the precipitate transformation section generates negative pressure in the circulated second precipitate to introduce at least one of gas and liquid.

2. The water treatment apparatus according to claim 1, characterized in that the gas is air.

3. The water treatment apparatus according to claim 1, characterized in that the precipitate alteration section supplies heat and at least one of an alkaline or acidic solution to the second precipitate to dissolve the flocs contained in the second precipitate.

4. The water treatment apparatus according to claim 1, characterized in that the precipitate alteration section supplies ozone to the second precipitate to decompose the flocs contained in the second precipitate.

5. The water treatment apparatus according to claim 1, characterized in that the precipitate alteration section irradiates the second precipitate with ultrasonic waves to break up the flocs contained in the second precipitate.

6. The water treatment apparatus according to claim 1, comprising at least one of the following: a second sediment amount control unit for controlling the amount of second sediment transferred from the second separation tank to the sediment alteration unit; and an altered sediment control unit for controlling the amount of altered sediment transferred from the sediment alteration unit to the first separation tank or upstream of the first separation tank.

7. The water treatment apparatus according to claim 6, characterized in that the second precipitate amount control unit controls the amount of the second precipitate so as to transfer all or part of the remaining amount, after deducting the amount of the second precipitate that maintains the microbial concentration in the reaction tank at a predetermined value, to the precipitate modification unit.

8. The water treatment apparatus according to claim 6, characterized in that the second sediment quantity control unit controls the amount of the second sediment so as to intermittently transfer the second sediment from the second separation tank to the sediment transformation unit, and continuously transfers the transformed sediment from the sediment transformation unit to the first separation tank or upstream of the first separation tank.

9. The water treatment apparatus according to claim 1, further comprising a modified precipitate control unit that determines the conditions for generating the modified precipitate to be transferred to the first separation tank or upstream of the first separation tank, based on the state of the wastewater, which is determined by the concentration of organic components in the wastewater, the flow rate of the wastewater, and the solid content of the second precipitate.

10. The water treatment apparatus according to claim 9, wherein the modified precipitate control unit calculates the amount of modified precipitate to be transferred to the first separation tank or upstream of the first separation tank based on the organic component concentration of the wastewater, the flow rate of the wastewater, and the solid content concentration of the second precipitate, and controls the amount of modified precipitate to be transferred to the first separation tank or upstream of the first separation tank according to the calculated amount of modified precipitate.

11. A water treatment apparatus according to any one of claims 1 to 10, A concentration device that concentrates the precipitate, which includes at least a primary precipitate, transferred from the water treatment device to obtain concentrated sludge, A digester that heats the concentrated sludge to decompose the organic matter contained in the concentrated sludge and generates digester gas, A water treatment system characterized by comprising the following features.

12. A first separation step involves receiving the wastewater and separating it into first effluent and first sediment, A reaction step in which the first effluent is received and the first effluent is brought into contact with microorganisms and reacted, A second separation step involves receiving the reaction water obtained in the above reaction step and separating the reaction water into second effluent and second precipitate, A precipitate alteration step in which at least a portion of the second precipitate is taken in, negative pressure is generated in the circulating second precipitate to introduce at least one of gas and liquid, thereby altering the state of the flocs, which are aggregates of microorganisms contained in the second precipitate, and an altered precipitate is produced. A mixing step involves mixing the generated altered precipitate with the wastewater to incorporate and precipitate organic matter in the wastewater, A water treatment method characterized by comprising the following:

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